This invention relates to a weighing system and more particularly to an improved method for sequentially compounding predetermined quantities of a plurality of constituents to form a batch.
Various types of batch weighing systems are well known and may be used, for example, to compound a plurality of ingredients which are melted to form glass. In one system, the various batch constituents are individually weighed prior to compounding in a batch receiving hopper. Either a separate scale is used for each constituent or the constituents are individually weighed on a single scale as they are sequentially fed into the batch receiving hopper. The cost of having a separate scale for each constituent may be prohibitively high and the final batch may be inaccurate due to variations between the scales. In either case, the final batch is subject to inaccuracies occurring from the apparatus used for feeding the various constituents to the scales.
In another type of batch weighing system, the various batch constituents are sequentially accumulated in a batch receiving hopper which is mounted either on a fulcrumed weight beam or on a strain guage for determining the weight of the hopper and its contents. The system may be controlled in response to either the total weight of batch constituents accumulated in the hopper or to the weight increment as each constituent is sequentially fed into the hopper. This type of control system is undesirable, however, because weight errors are accumulative. If the system is controlled by using only the weight increment of each successive constituent, accumulative errors are eliminated.
U.S. Pat. No. 3,595,328 discloses an improved automatic batch weighing system for compounding a series of batches containing predetermined measured quantities of various constituents. The constituents for each batch are successfully fed into a batch receiving hopper. The feeding of each constituent is adjusted by estimating the weight of an unpredictable dribble and by compensating for any deviation in the most recent batch compounded for a selected utilizing means to averge errors over a series of batches delivered to such utilizing means. Although the system disclosed in this patent is superior to prior art batch weighing systems, it does not use the individual constituent feeders at their maximum efficiency.